hwmon: (jc42) more helpful documentation

hwmon: (jc42) more helpful documentation

commit d5622f5b6c4671d1588ccc9056705366d4eb312a upstream.

The documentation lists standard numbers and chip names in excruciating
detail, but that's all it does.  To help mere mortals in deciding
whether to enable this driver, mention what this sensor is for and in
which systems it might be found.

Also add a link to the actual JC 42.4 specification.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>